By: Dr. Amr El-Dakroury
Dept. of Medical commission
Supreme Council of Health
:The etiology of Food-borne diseases
Food-borne diseases are those diseases that are the result
of exposure to pathogenic microorganisms, such as
bacteria, viruses and parasites, which tend to have acute
effects on human health.
However, chronic, and in some cases acute, food-borne
illness may also be caused by the presence of various
chemical substances including residues of pesticides and
veterinary drugs, unlawful food additives, mycotoxins,
biotoxins and radionuclides that enter the food
intentionally or unintentionally.
The problems :due to consumption of contaminated food
and its detrimental effect on human health .
:Epidemiology of FBD
WHO estimates that one in three people worldwide suffer
from a food-borne disease every year,
1.8 million die from severe food and waterborne diarrhea
Most of these illnesses are due to microorganisms and
chemical contaminants, which may occur naturally or be
introduced at some point along the food chain.
Campylobacter and Salmonella species account for over 90%
of all reported cases of bacteria related to food poisoning
As most cases of food borne disease are not reported, the true
dimension of the problem is unknown.
Today food safety is one of WHO’s top eleven priorities
:Food safety and security
The World Food Summit, organized by FAO in 1996,
recognized that access to safe food is in itself an element of
The World Health Assembly Resolution on Food safety
from May 2000 stated that :
1. Everyone should have the right to an adequate supply of
safe, nutritious food ,
2. Encourages WHO member states ‘‘to implement and keep
national and, when appropriate, regional mechanisms for
food borne disease surveillance’’
3. Governments should take the necessary measures to ensure
the availability of safe food for all in order to sustain the
health and economic development of their people.
The Response in Qatar
The Programme on Food- and Waterborne Diseases and
Zoonoses (FWD) in Qatar was set up with the establishment of
One of the key objectives for the programme is improving and
harmonizing the surveillance system in Qatar in order to increase
the scientific knowledge regarding etiology, risk factors and
burden of food- and waterborne diseases and zoonoses.
at present covers the following diseases: brucellosis,
campylobacteriosis, cholera, giardiasis, hepatitis A, salmonellosis,
shigellosis, toxoplasmosis, typhoid and paratyphoid fever,
Escherichia coli infection,
:Objectives of the FWD programme
Improving and harmonizing surveillance and
control interventions of FWD
Improving knowledge of prevention and control of
Strengthening SCH and Stakeholders capacities in
the area of FBD .
Improving early detection and coordinated
response to Qatar-wide FWD outbreaks ,as well as
control interventions .
Facilitating collaboration between public health,
municipality veterinary and food sectors
surveillance activities in Qatar
Food borne disease data collected through :
1. Routine surveillance activities
2. Outbreaks investigations and
3. Conducting special studies.
:Aims of FBD surveillance system
Food borne disease surveillance is essential for:
1. Estimating the burden of food borne diseases, and
2. Identifying priorities and setting policy in the
control and prevention of food borne diseases;
3. Detecting, controlling and preventing food borne
4. Identifying emerging food safety issues; and
evaluating food borne disease prevention and
Prevention and Control
There are an estimated 250 pathogens that can cause foodborne
Foodborne illness is defined as two or more cases of a similar illness
resulting from ingestion of a common food. It can result from consuming
foods contaminated with various pathogens. In most cases bacteria are
the major pathogen followed by viruses, then parasites.
However, natural or manufactured chemicals and toxins from
organisms can also cause foodborne illnesses.
The most commonly recognized foodborne infections are caused
by Campylobacter, Salmonella, E. coli O157:H7 and by caliciviruses
(better know as Norwalk viruses.)
Many foodborne illnesses are not recognized or go
unreported for a variety of reasons:
First, routine surveillance may not detect a mild
second, some of the same pathogens that cause
foodborne illness can also be transmitted in water or
from person to person.
Lastly, some pathogens are emerging and are not yet
identifiable or able to be diagnosed.
Considering these factors, the above listed number of
illnesses, hospitalizations and death may be obsolete.
High Risk Groups
Immunocompromised individuals are usually at
the greatest risk for these illnesses.
Transmission of foodborne pathogens occurs via the oral route.
How those pathogens contaminate food can vary based on the
organism, its reservoir, food handling/processing, and crosscontamination prior to serving.
Some organisms rely on a human reservoir, such as Norwalk-like virus,
Others have an animal reservoir such as Campylobacter, Salmonella, E. coli
0157:H7, Listeria, and Toxoplasma.
Contamination can occur at several points along
the food chain
On the farm or in the field
At the slaughter plant
At the point of sale
Animal products are not the
only food that can be
foodborne disease outbreaks
have occurred due to fruits and
This table indicates the many
possible sources for
contamination during the
processing of produce.
Although many pathogens can cause foodborne
illnesses, we will briefly cover those of greatest
impact. These may also be potential bioterrorism
agents for food sources.
Norovirus; Caliciviridae family
They are an important cause of sporadic gastrointestinal
disease outbreaks throughout the world. It is
considered the most common foodborne infectious
agent and an estimated 23 million cases occur each year.
Shed in human feces (up to 2weeks), vomitus.
Outbreaks in daycares, nursing homes, cruise ships
Contaminated raw shellfish.
Leading cause of bacterial diarrhea.
It is considered the leading bacterial cause of foodborne related
diarrhea affecting 2.4 million people each year (5-14% of all
diarrheal illnesses worldwide). Usually these are children under
the age of 5 and young adults (15-29 years of age).
Very few deaths are caused by this organism. Recently GuillainBarré Syndrome has been associated with a small number of
Campylobacter cases. This syndrome is the leading cause of acute
paralysis and develops 2-4 weeks after a Campylobacter infection
(after diarrheal signs disappear).
It is caused primarily by Campylobacter jejuni, but also C. fetus and
Raw or undercooked poultry
Infected animal or human feces
Poultry, cattle, puppies, kittens, pet birds
Diarrhea, abdominal cramps,
Duration: 2-5 days
Salmonella is a gram negative bacteria with many serotypes that
cause foodborne related illnesses. The ones we most commonly
associated with human foodborne illness are S. typhimurium and
They account for about 41% of all human cases reported
causes an estimated 1.4 million reported cases annually with 580
Raw poultry and eggs
Reptile pets: Snakes, turtles, lizards
Onset: 12-72 hours
Diarrhea, fever, cramps
Duration: 4-7 days
E. coli O157:H7
Escherichia coli is another major pathogen of foodborne related
Harmless strains of E. coli are found in nature, including the
intestinal tracts of humans and animals.
Diarrheal disease is caused by several different strains of harmful
E. coli. The most dangerous type is enterohemorrhagic E. coli
It gets its name because it can cause bloody diarrhea and can lead
to kidney failure in children or immunocompromised persons. E.
coli O157:H7 is the most common EHEC and its
enterohemorrhagic toxin is what actually causes the disease
E. coli O157:H7
Watery or bloody diarrhea, nausea, cramps
Onset: 2-5 days
Duration: 5-10 days
Hemolytic Uremic Syndrome (HUS)
Most commonly affecting children. HUS is the most
common cause of acute kidney failure in children.
Botulism is caused by a neurotoxin from Clostridium
This toxin causes flaccid paralysis and cranial nerve
deficits, and can lead to death.
The most common sources are home-canned foods,
fermented meats and honey
Double vision, drooping eyelids, difficulty speaking and
Onset: 18-36 hours
Shigellosis is also known as bacillary dysentery
Most cases are caused by Shigella sonnei. However, S. dysenteriae, S.
flexneri and S. boydii can also cause foodborne related illnesses.
Human fecal contamination of food, beverages, vegetables, water
Watery or bloody diarrhea, nausea, vomiting, cramps, fever
Onset: 2 days
Duration: 5-7 days
Toxoplasmosis is caused by an intracellular protozoan, Toxoplasma gondii
It is one of the three leading causes of death from a foodborne disease the
others were Salmonella and Listeria
Pregnant women and immunocompromised individuals, especially HIV
positive patients, are at the greatest risk of toxoplasmosis
The source of this protozoan include infected cats shedding in their feces,
soil, undercooked meat, and mechanical vectors such as cockroaches and flies
Clinical signs in humans can by asymptomatic to fever, headache, and swollen
lymph nodes. If the protozoan cysts develop in tissue, other more severe
clinical signs can be observed.
To prevent infection, gloves should be worn while gardening, changing cat
litter boxes and thoroughly washing raw fruits and vegetables before eating.
Irradiation and thoroughly cooking meat to 160oF internal temperature to
destroy the Toxoplasma cysts.
Sources >>>> Imported raspberries
Ready-to-eat meats, soft cheeses
Human abortions and stillbirths
Septicemia in young or low-immune
As stated earlier listeriosis is one of the 3 most common causes
of food borne related death.
Food producers and processors have implemented the HACCP
program in their operation to reduce the possibility of foodborne pathogens.
The Hazard Analysis Critical Control Point (HACCP) program is
used to monitor and control the production process by
identifying food safety hazards. Additionally, critical control
points in production, processing and marketing are identified.
Critical limits for each of these points is established and
monitored for food quality and safety. It is applied to the meat,
poultry and egg industries.
On Farm Strategies
To help control Salmonella Testing and removal this is done
Serologic testing, fecal or hide culturing of animals to identify carriers of
It is important to remember that vaccines are not 100% effective, and with the
various serotypes of bacteria and immune status of animals, they should be
used in accordance with other prevention methods.
Minimize rodents, wild birds
as they are often carriers of bacteria, will also help reduce the transmission.
Isolation of new animals
will also help decrease the chance of spread.
At the Slaughter Plant
FSIS (Food Safety Inspection Service)
has Identified target organisms :
Salmonella and E. coli
Removal of internal organs.
Minimize contact between carcasses.
Proper movement through facilities .
Cooking processes (proper time, temperature).
Drink pasteurized milk and juices.
Wash hands carefully and frequently
After using the bathroom.
Changing infant’s diapers.
Cleaning up animal feces.
Wash hands before preparing food.
Wash raw fruits and vegetables before eating
After contact with raw meat or poultry
Wash hands, utensils and kitchen surfaces.
Hot soapy water.
Defrost meats in the refrigerator
Cook beef/beef products thoroughly
Cook poultry and eggs thoroughly
Internal temperature of 160oF
Internal temperature of 170-180oF
Eat cooked food promptly
Refrigerate leftovers within 2 hours after
Store in shallow containers